Measuring Optical Transfer Functions of Lenses with the Aid of a Digital Computer

The problems involved in lens testing, as opposed to the testing of one lens under one set of conditions, are of sufficient magnitude and complexity that the use of a computer is almost imperative to make the job practical. A machine and method for evaluation of lenses is described which employs a digital computer as a major component, has no restrictions as to the quality of lenses which may be accommodated, and requires no precision targets or auxiliary optics of any type. The results are in a form directly applicable to predictions of performance of complicated systems where the lens is one of several linear dissipators. The reader is introduced to lens testing considerations and a brief discussion of methods, followed by a detailed description of a specific implementation and computerized approach. Next, the basic mathematics involved, including a practical procedure for truncating a Fourier series, are explained in some detail. Finally, examples of measured output and machine accuracy and stability examination are given.